"I can always tell a graduate class from an undergraduate class," observed the instructor in one of my graduate engineering courses at california state university in los angeles. "when i say, 'good afternoon,' the undergraduates respond, 'good afternoon." but the graduate students just write it down." “研究生班和本科生很容易就能区别开来，”在洛杉矶加利福利亚州立大学给我们研究生上工程学课的老师如此说。“我说‘下午好’，本科生们回答说‘下午好’。研究生们则把我说的话记在笔记本上。”